Mission Dart: “A nuclear explosion would only be used as a last resort to deflect an asteroid”, explains astrophysicist Patrick Michel – 20 Minutes

The shooting window of the Dart mission is wide, just in case: NASA engineers will have 84 days, until February 2022, to get it off the ground. But if the weather permits (and all the planets in space exploration are aligned), the Falcon 9 launcher from
SpaceX will take to the skies over California at 7:20 a.m. on Wednesday, Paris time. And Patrick Michel will have a front row seat.

The French astrophysicist, from the Côte d’Azur Observatory, is responsible for the cooperation between this project which aims
to deflect an asteroid and the European mission Hera, which will analyze the results. “I will coordinate the scientific support,” he explains from San Francisco where he took the time to answer questions from 20 minutes.

What must happen for the Dart mission to be a success?

At the beginning of spring 2022, the satellite must come to strike Dimorphos, the moon of the asteroid Didymos, to change its trajectory. We are talking about a kinetic impactor of 560 kg which will strike an object 160 m in diameter at more than 6 km / s [soit près de 22.000 km/h] 15 million kilometers from Earth. We hope to reduce its time of revolution around Didymos. But the effect is difficult to fully predict. Data will be available quickly, and the Hera mission, in 2026, will send a probe around Dydimos to observe in more detail everything that will have happened.

What will it be used for?

To learn to protect oneself from asteroids which could, one day, cross our orbit. It is a planetary defense project. While there is no known threat for the next century, the goal is to prepare for it. And it’s not like in Hollywood movies where only the American president takes matters into his own hands. We are here really in the case of an international project. He was even born in Europe and especially in France. NASA and ESA (European Space Agency) are involved but there is also Japan. They provided one of Hera’s instruments. There is no world authority for this planetary defense. With these missions, we only provide plans to know how to react.

In Hollywood films, it is more often a question of nuclear explosion to get rid of the threat of a collision …

This is not a ruled out solution. But that would only be a last resort. Only if we haven’t seen it coming and there is little time left. The kinetic impactor, like Dart’s, is the gentle method, when you have had time to prepare.